1. Field of the Invention
This invention relates to a recording and/or reproducing apparatus having a high fail-safe effect.
2. Description of the Related Art
In the recording apparatus of the kind arranged to use a rotary record bearing medium, such as a magnetic disc or a magnetic drum and to record by means of a moving head a unit length of information, such as one field or frame portion of a video signal, in each of recording tracks which are formed in a concentric or annular shape on the medium according as the information is recorded, the head must be correctly positioned on the medium at an unrecorded part thereof before recording the information in order to avoid double or overlapped recording.
In view of this, some of known apparatuses of the above stated kind have been arranged to detect prior to recording the presence or absence of any record in each recording position on the record bearing medium; to shift the head to a next recording position in the event of detection of any existing record; to repeatedly perform the head shifting action as necessary before the head comes to a desired unrecorded part on the medium; and to permit recording after the head is correctly positioned. Such arrangement has been disclosed, for example, in Japanese Patent Application Laid-Open No. SHO 54-140516 and in U.S. patent application Ser. No. 030,930, filed Apr. 17, 1979 now abandoned and assigned to the assignee of the present invention.
In the case of the apparatus arranged in the above stated manner, if a control sequence is set up, for example, to shift the head to a next recording position either upon completion of recording in one recording position or before recording in the next position, the present position on the record bearing medium of the head would serve as a memory relative to the next recording position on the medium. Therefore, even when the power supply for the apparatus is switched off or, in the event of a portable apparatus, when the power source battery thereof is taken out for replacement or charging or when the battery voltage drops to an unserviceable level lower than a threshold value, the possibility of any double recording on the same medium can be eliminated and also further recording can be accomplished without leaving any unnecessary unrecorded part (or a vacant track or tracks) on the basis of the present position of the head as long as the head has not been moved from the present position during an interval time between the present recording and further recording.
However, if the record bearing medium is replaced with another record bearing medium while the power supply is somehow cut off, the present head position becomes totally meaningless. Therefore, recording under this condition might result either in a double record, overlapped records or vacant tracks. To avoid such inconvenience, the head must be positioned at an unrecorded part on the record bearing medium every time the power supply is switched on. However, this head positioning action is meaningless in cases where the record bearing medium remains unreplaced. Besides, it impairs by and large the quick recording operability of the apparatus (corresponding to the so-called quick shooting operability of cameras). Further, in the case of a portable type apparatus, the consumption of the power source battery is quickened by such arrangement. A problem similar to this likely arises in the case of an apparatus arranged to necessitate readjustment of recording conditions such as change-over of the head to be used from one head over to another according to the properties and kind of the record bearing medium.
To solve this problem, there has been proposed a recording apparatus which permits an interchange of record bearing media and is equipped with some means for mechanically memorizing and storing information on that a record bearing medium has been taken out or replaced with a new record bearing medium. The details of this apparatus are as disclosed in U.S. patent application Ser. No. 826,117, which was filed Feb. 5, 1986, now abandoned assigned to the assignee of the present invention and corresponding to Japanese Patent Application No. SHO 60-22633. When the record bearing medium is replaced with another medium, the above stated memory means mechanically memorizes this fact. In next recording, confirmation is made on the basis of the content of the mechanical memory means as to whether the record bearing medium has been replaced. Then, a head resetting action for readjustment of the position of the head to an unrecorded part of the medium is performed only when the fact that the medium has been replaced is thus confirmed.
In that instance, however, if this mechanical memory means is reset before detection of a recordable part of the record bearing medium, occurrence of some power supply trouble (consumption, replacement, or a temporarily cut off state due to an erroneous operation of the battery) or mixing-in of some external noise or the like before detection of the recordable part would make an adequate head positioning action impossible.
Further, in resetting the head at an unrecorded part in the above stated manner to initialize thereby the apparatus in the recording mode, generally a considerably long period of time is required before the start of an actual image sensing recording operation. During this period, therefore, the power source is generally consumed to a great degree. Whereas, there is a strong desire to have the apparatus arranged to enable the operator to monitor a picked-up image of an object immediately after completion of the initializing process.
Further, a recording apparatus of the above stated kind necessitates a power supply, like a still picture camera. However, in taking out the record bearing medium, if the power supply is not switched on, the head would remain at an unrecorded part of the record bearing medium. Under that condition, the medium taking-out action would injure the head. Further, when another record bearing medium is inserted in place of the medium taken out, the head is located at a part corresponding to a first unrecorded part of the previous medium as viewed from the outer circumferential side thereof. Therefore, after a release switch is pushed, a look-up action must be performed for a first unrecorded part of the newly inserted medium. While the image sensing or recording apparatus is usable without any other devices for image sensing and recording, it can be variously arranged, for example, to be capable of performing a reproducing function and/or to permit remote control over illumination, etc. by connecting some adapter and some accessory to the apparatus.
In such a case, the adapter and the accessory consume some amount of electric energy. If they are provided with no battery for their own use but are arranged to receive a power supply from the power source of the apparatus, then, this presents a problem with regard to the timing of the power supply, because: Constant power supply would shorten the life of the battery, would cause corrosion of connectors. It also would shorten the serviceable life of electric parts and degrade the reliability of them. Some of these problems would remain unsolved even if the adapter and the accessory is provided with some power source for their own use.
Further, in accordance with the head positioning method mentioned above, if some recording track is erased in an intermediate part of the record bearing medium, the head is first positioned for the erased track. In this instance, the head is shifted to a next recording position after completion of recording in the first position. Then, in shifting the head to the next position, the presence or absence of an existing record is also examined and determined. In other words, in the event of a vacant track located in an intermediate part, in order to avoid double recording, a check must be made for the presence or absence of any existing record every time the head is shifted. In that event, an excessively long period of time is required before next recording becomes possible with the head shifted to an unrecorded part. Then, a recording chance (corresponding to the so-called shutter chance of a camera) would be missed or continuous recording, such as a continuous still video recording for several consecutive fields of frames, would become impossible because of such a long period of time.